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United States Patent |
6,229,765
|
Rabi
|
May 8, 2001
|
Electronic sunrise-dependent timepiece
Abstract
An electronic sunrise-dependent timepiece, comprising an oscillator circuit
for generating clock pulses at a predetermined frequency and a clock
circuit coupled to the oscillator circuit for generating minutes and hours
and calendar data. An offset correction circuit coupled to the clock
circuit and being responsive to a current value of calendar data adds a
respective offset to the minutes and hours data so as to generate a
sunrise-dependent time of day for display on a suitable display device.
Inventors:
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Rabi; Moshe (Herzelya, IL)
|
Assignee:
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RM-IC Telepathy Ltd. (Herzelya, IL)
|
Appl. No.:
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266022 |
Filed:
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March 11, 1999 |
Foreign Application Priority Data
Current U.S. Class: |
368/156; 368/28; 368/185; 368/187 |
Intern'l Class: |
G04F 005/00; G04B 019/26; G04C 009/00 |
Field of Search: |
368/185,187,28,29,157,156
|
References Cited
U.S. Patent Documents
3827233 | Aug., 1974 | Villa Eschevarria et al.
| |
4671672 | Jun., 1987 | Hubner.
| |
4763311 | Aug., 1988 | Marvosh | 368/157.
|
4920365 | Apr., 1990 | Marx et al. | 368/187.
|
4956826 | Sep., 1990 | Coyman et al. | 368/28.
|
4995020 | Feb., 1991 | Mitchell | 368/185.
|
5926441 | Jul., 1999 | Zinsmeyer et al. | 368/28.
|
6011755 | Jan., 2000 | Mulhall et al. | 368/28.
|
Foreign Patent Documents |
3708578 | Oct., 1987 | DE.
| |
196 53 306 | Jun., 1998 | DE.
| |
0447849 | Sep., 1991 | EP.
| |
0762244 | Mar., 1997 | EP.
| |
Other References
JP361017090A, Muroi et al., Yearly Solar Time Switch, abstract, Jan. 1986.
|
Primary Examiner: Miska; Vit
Assistant Examiner: Goodwin; Jeanne-Marguerite
Attorney, Agent or Firm: Browdy and Neimark
Claims
What is claimed is:
1. An electronic sunrise-dependent timepiece, comprising:
an oscillator circuit for generating clock pulses at a predetermined
frequency,
a clock circuit coupled to the oscillator circuit for generating minutes
and hours and calendar data,
an offset correction circuit that includes a look-up table storing
respective offsets to be added to the hours and minutes data depending on
a pre-calculated time of sunrise at a range of calendar data, the offset
correction circuit being coupled to the clock circuit for deriving the
respective offset from the look-up table and adding the respective offset
to the minutes and hours data so as to generate a sunrise-dependent time
of day, and
a display circuit coupled to the clock circuit for displaying the
sunrise-dependent time of day, wherein
the offset derived by the offset correction circuit is an incremental
offset that is fixedly added to a currently displayed sunrise-dependent
time at predetermined time intervals.
2. The sunrise-dependent timepiece according to claim 1, further including
a set switch coupled to the clock circuit for setting the calendar data to
a desired value.
3. The sunrise-dependent timepiece according to claim 1, wherein the offset
correction circuit is adapted to add the offset to the minutes and hours
data at a predetermined time of day at specified time periods.
4. The sunrise-dependent timepiece according to claim 1 wherein the offset
correction circuit further includes
an encoding means for encoding an adjustment time based on a predetermined
time for effecting the offset correction and a specific time period, and
a decoder coupled to the clock circuit for comparing the clock data with
the adjustment time;
the offset correction circuit being responsive to an output from the
decoder changing from a first level to a second level, for adding to an
respective offset to the clock data.
Description
FIELD OF THE INVENTION
This invention relates to digital electronic timepieces.
BACKGROUND OF THE INVENTION
Digital watches and clocks have become so commonplace that fully integrated
clock circuits are widely available requiring little more than the
connection of an external battery, a display and suitable set switches to
construct a fully functional timepiece. Such integrated circuits are based
on a highly accurate oscillator usually employing a quartz crystal and a
counter. Suitable registers are connected to the counter and have
respective outputs which are adapted to toggle after a predetermined
number of pulses have been counted. In this manner, stock can be taken
separately of the passage of seconds, minutes and hours. Likewise, after
suitable initialization, track can be taken of the successive passage of
twenty-four hour periods, thus allowing calendar data also to be
maintained and displayed. The outputs are converted from binary-coded
decimal format for display on 7-segment displays. Usually, an alarm clock
function is also provided so as to alert the user of the watch at a preset
time of day, typically so as to awaken the user from sleep.
Currently available digital watches, once set by the manufacturer or user,
maintain an accurate record of the time and calendar data but take no
account of the small seasonal changes in sunrise time which occur in any
given location. Such changes occur continuously and, unless corrected for,
are cumulative over a period of time. More specifically, sunrise occurs
later throughout the winter until mid-winter and occurs earlier throughout
the summer until mid-summer.
The cumulative change in sunrise time, over a period of time, results in an
increasing seasonal discrepancy between the time of sunrise and the time a
person must start the day. This is unpleasant because most people prefer
to rise when it starts to get light outside. Thus, if this requirement is
met at the start of winter, then owing to the increasing delay in time of
sunrise throughout winter until the onset of mid-winter, people who rise
at the same time each day will be constrained to do so when it is
increasingly dark outside. On the other hand, in summer people tend
naturally to awaken earlier than necessary owing to the increasing advance
in time of sunrise throughout summer.
In many countries it is common to make a one-off correction for the
cumulative delay and advance in sunrise time by "moving the clock" forward
in summer and backward in winter, usually by one hour at a given time on a
specified day at the start of summer and winter. Obviously, any day may be
specified as to when the necessary correction or corrections should be
made and this is usually determined by each government in an effort to
make maximum use of available daylight, thereby reducing the need for
artificial illumination and thereby saving energy. Such considerations may
encourage seasonal corrections to be made more than once each season.
Regardless of how many times a season correction is made, it frequently
plays havoc with the internal bio-clock of the workforce. The reason for
this is obvious when the clock is moved forward in summer, because the
adjustment is normally effected at midnight or in the middle of the night
causing people to lose an hour's sleep. However, in the winter the
adjustment is no less convenient for two reasons. First, people normally
go to bed an hour later since they know that nominally they will have the
same number of hours'sleep. Thus, at best, they receive no benefit from
the hour gained. Usually, however, their body wakens at the normal time to
which they have become accustomed which is now an hour earlier than
necessary. So they lose on both counts and suffer from tiredness until
their bodies become accustomed to the new regimen.
This inability to adjust to a sudden change in nominal time is due to the
fact that, in order to be effective, a large increment of at least one
hour, must either be added or subtracted from the nominal time once each
season. The actual change in time of sunrise is, of course, much more
gradual but it is not very practical to make many small adjustments
throughout each season.
In addition to time changes caused by seasonal effects, it is also known
that sunrise changes with longitude and this gives rise to
geographic-dependent time changes according to one's longitude. Here, too,
each adjacent time zone has a time difference of one hour, either plus or
minus depending on the relative longitude of the adjacent zones. People
who travel from one time zone to another must set their watches
accordingly and the cumulative time difference in travelling between
remote zones, and thereby crossing many intermediate time zones results in
the phenomenon well-known as "jet lag" with its attendant exhaustion.
Whilst there is no way to compensate for jet lag, the patent literature has
addressed the need to adjust one's watch when crossing adjacent geographic
time zones. Thus, U.S. Pat. No. 3,827,233 in the name of Villar discloses
a mechanical geographic timepiece wherein the minute hand is rotated, via
a worm and bevel gear system in accordance with the inclination of the
polar axis of the earth. This allows for automatic compensation for
changing longitude as the timepiece is transported through different time
zones.
U.S. Pat. No. 4,671,672 to Hubner discloses a universal time clock
employing a globe which is driven by the hour tube of a left-hand rotating
clockwork.
Both of these patents describe cumbersome mechanical clockwork systems for
compensating for changes in longitude and are relevant only to the extent
that such changes are also due to differences in time of sunrise. Neither
of these references describes a portable timepiece which compensates for
seasonal changes in time of sunrise in a fixed geographic location so as
to enable a user or a community of users to operate according to time of
sunrise.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a portable, electronic
timepiece which automatically compensates for seasonal changes in time of
sunrise.
According to the invention there is provided an electronic
sunrise-dependent timepiece, comprising:
an oscillator circuit for generating clock pulses at a predetermined
frequency,
a clock circuit coupled to the oscillator circuit for generating minutes
and hours and calendar data,
an offset correction circuit coupled to the clock circuit and being
responsive to a current value of calendar data for adding a respective
offset to the minutes and hours data so as to generate a sunrise-dependent
time of day, and
a display circuit coupled to the clock circuit for displaying the
sunrise-dependent time of day.
Preferably, the sunrise-dependent timepiece further includes a selector
switch for selectably switching the offset correction circuit to the clock
circuit so as to allow display of either an uncompensated time of day or
the sunrise-dependent time of day.
Optionally, a set switch is coupled to the clock circuit for setting the
calendar data to a desired value. This allows initialization of the
timepiece by an end-user according to the actual date on which the
timepiece is set and obviates the need for pre-calibration by the
manufacturer.
Optionally, the offset correction circuit is adapted to extract the offset
from a look-up table and add the offset to the minutes and hours data once
daily at a predetermined time each day. However, the offset may be
calculated using a pre-programmed function and adjustment can be performed
at other fixed time intervals, e.g. once weekly if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to understand the invention and to see how it may be carried out
in practice, a preferred embodiment will now be described, by way of
non-limiting example only, with reference to the accompanying drawings, in
which:
FIG. 1 is a block diagram showing functionally an electronic
sunrise-dependent timepiece according to a first embodiment of the
invention;
FIG. 2 is a block diagram showing functionally an electronic
sunrise-dependent timepiece according to a second embodiment of the
invention; and
FIG. 3 shows graphically seasonal sunrise data which is stored as a series
of offsets in a look-up table within the timepiece.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 1 shows functionally an electronic timepiece depicted generally as 10
comprising an oscillator circuit 11 for generating clock pulses at a
predetermined frequency. A clock circuit 12 is coupled to the oscillator
circuit 11 for generating minutes and hours and calendar data. The
oscillator circuit 11 may employ a quartz crystal and may be integrated
with the clock circuit 12 as a single component, in known manner. Coupled
to the clock circuit is a look-up table 13 for storing respective offsets
to be added to the minutes and hours data depending on a pre-calculated
time of sunrise at a range of calendar data. An offset correction circuit
14 is selectably coupled to both the clock circuit 12 and the look-up
table 13 by means of a selector switch 15 and is responsive to a current
value of calendar data at a predetermined time period for adding a
respective offset to the hours and minutes data so as to generate a
sunrise-dependent time of day, and a display circuit 16 is coupled to the
clock circuit 12 for displaying the sunrise-dependent time of day. The
display circuit 16 may comprise a digital or analog display module
connected to a suitable driver.
The selector switch 15 allows the offset correction circuit to be
selectably switched to the clock circuit so as to allow display of either
an uncompensated time of day or the sunrise-dependent time of day, as
required. A pair of set switches 17 and 17' are also coupled to the clock
circuit 12 for setting the time and calendar data to a desired value,
thereby allowing initialization of the timepiece by an end-user according
to the actual date on which the timepiece is set and obviating the need
for pre-calibration by the manufacturer. Typically, the set-switches 17
and 17' are standard functions of an integrated clock circuit.
In such an arrangement, the look-up table 13 stores a cumulative offset for
each addressable calendar date and the offset correction circuit 14 is
thus adapted to add the cumulative offset to the minutes and hours data.
As a result, the selector switch 15 allows the displayed time to be
toggled between regular time and sunrise-compensated time, as required.
FIG. 2 shows functionally an electronic timepiece depicted generally as 20
comprising a clock circuit 21 containing an integral oscillator circuit 22
for generating clock pulses at a predetermined frequency. The oscillator
circuit 22 is coupled to a seconds counter 23, to a minutes counter 24 and
to an hours counter 25 for generating seconds, minutes and hours data,
respectively. The hours data is, in turn, coupled to a calendar 26 for
generating calendar data. The seconds counter 23, minutes counter 24 and
hours counter 25 as well as the calendar 26 are coupled to a display
circuit 27 typically being a LCD for displaying time and date digitally by
means of 7-segment displays. However, an analog display may also be
employed using a suitable driver. The date and time may be set remotely by
means of suitable set switches (not shown) coupled to the clock circuit
21.
Selectably coupled to the minutes counter 24 and hours counter 25 by means
of a selector switch 28 is an offset correction circuit 29 for adding
respective incremental offsets to the minutes and hours data,
respectively, depending on a pre-calculated time of sunrise at a range of
calendar data stored in a look-up table 30. A decoder 31 is coupled to the
seconds counter 23, the minutes counter 24 and to the hours counter 25 for
generating an offset enable signal OE at an output thereof at a
pre-programmed time of day. Optionally the decoder 31 may also be coupled
to the calendar 26 in order that the enable signal OE be produced on
specified dates or days only, and not every day. The output of the look-up
table 30 is fed to respective inputs of a pair of AND gates 32 and 33
having inputs connected to the output of the decoder 31 and also to one
pole of the selector switch 28 which is connected to the positive power
supply Vcc via a suitable pull-up resistor 34. The other pole of the
selector switch 28 is connected to GND. An address bus 35 connects the
look-up table 30 to the decoder 31 so as to allow the appropriate entry in
the look-up table to be read for a specific calendar date.
The offset correction circuit 29 operates as follows. When the selector
switch 28 is closed, logic "0" is fed to the AND gates 32 and 33.
Consequently, their outputs are logic "0" regardless of the output of the
decoder 31. However, when the enable signal OE at the decoder output is
logic "1" and the selector switch 28 is opened, the digital incremental
offsets in the look-up table 30 for the current time period are fed by the
AND gates 32 and 33 to the minutes and hours counters 24 and 25,
respectively by MSET and HSET so as to increment their respective counts
by the appropriate minutes and hours offsets. By such means, for so long
as the selector switch 28 remains open, appropriate increments are added
to the minutes and hours counters 24 and 25 at each pre-programmed time
period and a sunrise-dependent time of day is displayed by the display
circuit.
If the selector switch 28 is now closed, logic "0" is again fed to the AND
gates 32 and 33, thereby disabling the offset correction circuit 29.
However, unlike the first embodiment shown in FIG. 1, the time shown on
the display circuit 27 does not automatically return to the regular time
since, in this case, the minutes and hours counters 24 and 25 are
irreversibly incremented by the offset correction circuit 29. Therefore,
the timepiece 20 must be manually reset using the set switches (not shown)
coupled to the clock circuit 21 if regular time is required. The set
switches also allow the calendar data to be set to a desired value,
thereby allowing initialization of the timepiece by an end-user according
to the actual date on which the timepiece is set and obviating the need
for pre-calibration by the manufacturer.
The timepiece 20 shown in FIG. 2 thus differs from the timepiece 10 shown
in FIG. 1 in several ways. In the second embodiment, the offset correction
circuit 29 is adapted to add the offset to the minutes and hours counters
24 and 25 at a predetermined time of day either daily or at any other
pre-programmed time period. For example, if the predetermined time of day
when the adjustment is effected is 3:00 and on a particular date the
required adjustment is +2', 42" then the displayed time would change from
2:59:59 to 3:02:42. Such a small difference occurring when most users are
asleep would, of course, cause no disturbance to the end-user. Associated
with this, the offsets stored in the look-up table 13 shown in FIG. 1 are
cumulative offsets which are added to the current time of day prior to
display. In contrast, the offsets stored in the look-up table 30 shown in
FIG. 2 are incremental and are added to the minutes and hours counters 24
and 25. Therefore, once sunrise time is enabled, the minutes and hours
counters 24 and 25 are constantly incrementally adjusted and therefore not
amenable to toggling between regular and sunrise time.
The use of incremental offsets in the second embodiment further leads to
the storage in the look-up table of small changes which may therefore be
accurate to within several seconds when the adjustment is made to the
seconds counter 23 and the minutes counter 24 instead of to the minutes
counter 24 and the hours counter 25. For such accuracy using cumulative
offsets much greater memory capacity would be required.
Likewise, in the first embodiment, there is no fixed time when adjustment
is made since this is user-dependent. However, in the second embodiment
shown in FIG. 2, adjustment is effected at a fixed time of day
(constituting the adjustment time) which is typically set during
manufacture but could feasibly be set by the end-user using the
set-switches.
FIG. 3 shows graphically seasonal sunrise data for Israel which is stored
as a series of offsets in the look-up table 13. Thus, for each calendar
date shown on the x-axis, a corresponding positive or negative offset
shown on the y-axis is stored in the look-up table 13. In use, the clock
circuit 12 produces data indicative of the current date (constituting
calendar data), which serves as the address to the look-up table 13 or 30.
By such means, the required offset is derived and added to the time data
generated by the clock circuit 12 prior to display. It will be understood
that sunrise data is dependent on latitude and therefore changes from one
country to another and even within the same country. If desired, multiple
look-up tables can be provided so as to adapt the timepiece for use at
different geographic locations.
The sunrise data shown in FIG. 3 is shown approximately for weekly time
intervals. In reality, it will be appreciated that the graph is cyclical
and repeatable so that, for example, the sunrise times at the two
end-points, both of which show the sunrise times at March 22, must be
identical. The actual data stored in the look-up table 13 or 30 may, of
course, have higher resolution, for example based on daily variations in
sunrise time. Alternatively, the sunrise time for a particular calendar
date may be derived by interpolating between the two entries in the
look-up table corresponding to the two dates closest thereto. This allows
high accuracy whilst obviating the need for high resolution requiring a
correspondingly large memory.
It should be noted that the internal structure of the look-up tables is
different in the two embodiments. In the look-up table 13 shown in FIG. 1,
cumulative offsets are stored each corresponding to the required absolute
offset for the corresponding time period. As may be seen from the curve
shown in FIG. 3, their nominal values get progressively larger until
mid-winter and then decrease so as to reach a minimum at mid-summer. The
offsets are preferably stored relative to an average DC level such that
they are positive in summer and negative in winter. However, in the
look-up table 30 shown in FIG. 2, incremental offsets are stored each
relative to the previous offset. Thus, from mid-summer until mid-winter
the incremental offsets are negative and change to positive from
mid-winter until mid-summer, their magnitudes being fairly constant and
small. As a result, each addressable memory location in the look-up table
13 must be able to store higher values than those in the look-up table 30,
thus requiring a larger memory and, as noted above, resulting in lower
accuracy.
It will be appreciated that modifications may be made to the invention
without departing from the scope thereof as defined in the appended
claims. For example, in the second embodiment, instead of using a decoder
to determine when to effect the adjustment, software can be embedded
within the clock circuit 21.
Likewise, the adjustment time can be stored in a separate memory module or
could be encoded using other encoding means, such as suitable logic
elements or switches, all as is well known in the art.
It will further be appreciated that whilst, as described, the adjustment is
made when the offset enable goes HIGH, this is merely a design choice and
the required adjustment could equally well be made LOW enable.
Finally, whilst a look-up table is used in the preferred embodiments, it
will be appreciated that the required offsets can be calculated based on
current calendar data using a suitable pre-programmed function.
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